Dunes on Pluto?

Finally, two months after the New Horizons spacecraft flew by the dwarf planet at close range, new higher resolution images have arrived.

It has taken that long for NASA to download them. The transfer speed of data from the spacecraft at 2,000 bits per second makes an old dial-up modem with its 56,000 bits per second look like a speed demon.

It will take NASA a year to transfer all the photos and data. The dump began arriving over the Labor Day weekend. Some of the pictures that NASA released were not single snapshots but compilations synthesized from multiple photos.

Judging by the first, crisp digital close-up images, the wait was worth it. They reveal a planet not frozen in place but with a complex landscape still developing. …

The photos taken from New Horizons’ closest approach of Pluto on July 14 — at about 50,000 million miles away — reveal some surprises.

For example, there may even be dunes blown up by winds. But that would seem impossible on a planet with barely an atmosphere.

“Seeing dunes on Pluto — if that is what they are — would be completely wild, because Pluto’s atmosphere today is so thin,” said astronomer William B. McKinnon from Washington University in St. Louis.

“Either Pluto had a thicker atmosphere in the past, or some process we haven’t figured out is at work. It’s a head-scratcher.”

And those gargantuan blocks of ice the size of mountains might be floating in flows of frozen nitrogen.

The spacecraft also picked up nice images of Pluto’s moons. Photos of Charon — the largest one — reveal a mammoth crack, a tectonic fracture.

Unlike the icy moons of giant planets, Pluto cannot be heated by gravitational interactions with a much larger planetary body. Some other process must be generating the mountainous landscape.

“This may cause us to rethink what powers geological activity on many other icy worlds,” says GGI deputy team leader John Spencer of the Southwest Research Institute in Boulder, Colo.

The mountains are probably composed of Pluto’s water-ice “bedrock.”
Although methane and nitrogen ice covers much of the surface of Pluto, these materials are not strong enough to build the mountains. Instead, a stiffer material, most likely water-ice, created the peaks. “At Pluto’s temperatures, water-ice behaves more like rock,” said deputy GGI lead Bill McKinnon of Washington University, St. Louis.

The close-up image was taken about 1.5 hours before New Horizons closest approach to Pluto, when the craft was 47,800 miles (77,000 kilometers) from the surface of the planet. The image easily resolves structures smaller than a mile across.